I am now running Fedora 24 in a virtual machine using Virtual Machine Manager instead of VirtualBox. This is one of two relatively unknown open source virtual machine programs you can get in the Ubuntu repositories. (The other is Boxes.) Both use QEMU/KVM as the virtual engines. Fedora seems to run on this much better then it does on Virtualbox. It was easy to set up (apparently Boxes is even easier) and you can change the monitor resolution on the fly with a setting instead of by resizing the window. You can also run it full-screen. The one disadvantage: it lacks the tools to communicate with the host OS, although there is apparently a way you can do so by adding another program. Virt-manager is a great way to test out a distro; worth a try if you haven't used it yet.
Here (https://search.yahoo.com/search?fr=spigot-nt-gcmac&ei=utf-8&ilc=12&type=453483&p=gnome-boxes%20youtube) is a good video on Gnome-boxes, with a guy demoing it on Peppermint.